Strepsirrhini
Encyclopedia
The clade
Strepsirrhini (New Latin
, from Greek strepsis, "a turning" and the stem of rhis, "nose") is one of the two suborders of primate
s. Madagascar
's only non-human primates are strepsirrhines, and others can be found in southeast Asia
and Africa
. The scientist given credit for the name, Étienne Geoffroy Saint-Hilaire
, named it for the retention of the rhinarium
, a trait characterized as a wet nose, generally present in mammals. In his catalog of features attributed to the Strepsirrhini, he lists "Les narines terminales et sinueuses" (translated "sinuous, twisted or curly nostrils").Some confuse the comb-shaped lower incisors with the nostrils to arrive at "comb-shaped", and some confuse the nostrils with the nose and strepsis with strephein, "to bend ot turn" to arrive at "bent nose." The nose is not bent, nor are the nostrils comb-shaped, but the nostrils of a rhinarium do generally feature sinuous openings. Strepsirrhines are often characterized by their wet noses, but the etymology of their group name refers to the sinuous openings of the rhinarium's nostrils.
Strepsirrhines are considered by primatologists to have more evolutionarily ancestral features and adaptations than their haplorhine ("dry-nose", in Greek "simple nose") cousins. Their moist nose is connected to the upper lip, which is connected to the gum, limiting the facial expressions they can manage. Their brain to body ratio tends to be smaller, indicating a lower intelligence. Their brain's olfactory lobes are larger, lending to the notion that they have a stronger reliance on smell. Their snouts are generally elongated, giving them a dog
-like appearance, although this is true of some monkey
s, too. Strepsirrhines have a postorbital bar
, unlike haplorrhines. The strepsirrhines have also retained the ability to enzymatically manufacture vitamin C, which has been lost by all the haplorrhines, including the Tarsiidae.
With the exception of the aye-aye
, all strepsirrhines have a toothcomb
—tightly clustered incisor
s and canine teeth—that is used for grooming. Another grooming adaptation is a toilet-claw
on the second toe of all strepsirrhines, while the big toe is widely separated from the others, allowing a vise-like grip for locomotion.
About 75% of species are nocturnal and all of these have a tapetum
, a shiny, reflective layer in the backs of their eyes, although several diurnal
species, such as the ring-tailed lemur
, have it, as well. Many of the nocturnal species also have very sensitive hearing and ears they can move independently, allowing them to capture sounds even better.
Strepsirrhine reproduction differs greatly from haplorrhine reproduction. Instead of an individual cycle, strepsirrhines have a breeding season. They also have a litter of offspring and the females have a Y-shaped (bicornate) uterus and multiple sets of nipples.
The suborder Strepsirrhini is composed of seven families split into two groups. The first group is the infraorder Lemuriformes, five families of primates typically called lemur
s. The other two families are split with the loris
es, potto
s and the galago
s in the infraorder Lorisiformes
.
As recently as 2005, the aye-aye
was tentatively placed in its own infraorder (Chiromyiformes). It was uncertain whether this unique primate split off from the ancestral strepsirrhine line before the lemurs and lorises, or after. If the aye-aye represents a group that is ancestral to all the rest of Strepsirrhini, then it evolved away from the strepsirrhine line between 63 million years ago (mya) (when the strepsirrhines split from the primitive primate line) and 50 mya (the lemur/loris split). If Chiromyiformes is to be considered as the sister only to the lemurs, then it must have evolved after the lemur/loris split 50 mya. In 2008, the aye-aye and its family, Daubentonia, were placed back in infraorder Lemuriformes, making it the fifth lemur family. Molecular research had shown that Aye-ayes were basal to the lemuriform clade
.
Early classification schemes broke the Primate order into the suborders Prosimii (prosimian
s) and Anthropoidea (simian
s - monkeys and ape
s). However, the prosimian tarsier
s have been shown to be more closely related to the simian
s. The remaining "prosimians" are now placed in Strepsirrhini, and tarsiers are now united with anthropoids (simians) in Haplorrhini.
Some classifications split Strepsirrhini directly into four superfamilies: Daubentonioidea, Lemuroidea, Loroidea (including Cheirogaleidae) and Indroidea. However, significant evidence suggests Cheirogaleidae is not related to the lorises, and that Indridae is sister-group to Lemuridae.
The strepsirrhine phylogeny has also been elucidated by retrotransposon
presence/absence data
.
The adapid
s are an extinct polyphyletic grouping that were most certainly prosimian
s and closely related to the strepsirrhines. The omomyid
s are another extinct group of prosmians, but they are believed to be haplorrhines, closely related to the tarsiers, but an outgroup to the rest of the haplorrhines.
As of 2010, there are 125 species of extant strepsirrhine primates, over three-quarters of which are lemurs from Madagascar
.
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
Strepsirrhini (New Latin
New Latin
The term New Latin, or Neo-Latin, is used to describe the Latin language used in original works created between c. 1500 and c. 1900. Among other uses, Latin during this period was employed in scholarly and scientific publications...
, from Greek strepsis, "a turning" and the stem of rhis, "nose") is one of the two suborders of primate
Primate
A primate is a mammal of the order Primates , which contains prosimians and simians. Primates arose from ancestors that lived in the trees of tropical forests; many primate characteristics represent adaptations to life in this challenging three-dimensional environment...
s. Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
's only non-human primates are strepsirrhines, and others can be found in southeast Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
and Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
. The scientist given credit for the name, Étienne Geoffroy Saint-Hilaire
Étienne Geoffroy Saint-Hilaire
Étienne Geoffroy Saint-Hilaire was a French naturalist who established the principle of "unity of composition". He was a colleague of Jean-Baptiste Lamarck and expanded and defended Lamarck's evolutionary theories...
, named it for the retention of the rhinarium
Rhinarium
The rhinarium is the moist, naked surface around the nostrils of the nose in most mammals. In actual scientific usage it is typically called a "wet snout" or "wet nose" from its moist and shiny appearance...
, a trait characterized as a wet nose, generally present in mammals. In his catalog of features attributed to the Strepsirrhini, he lists "Les narines terminales et sinueuses" (translated "sinuous, twisted or curly nostrils").Some confuse the comb-shaped lower incisors with the nostrils to arrive at "comb-shaped", and some confuse the nostrils with the nose and strepsis with strephein, "to bend ot turn" to arrive at "bent nose." The nose is not bent, nor are the nostrils comb-shaped, but the nostrils of a rhinarium do generally feature sinuous openings. Strepsirrhines are often characterized by their wet noses, but the etymology of their group name refers to the sinuous openings of the rhinarium's nostrils.
Strepsirrhines are considered by primatologists to have more evolutionarily ancestral features and adaptations than their haplorhine ("dry-nose", in Greek "simple nose") cousins. Their moist nose is connected to the upper lip, which is connected to the gum, limiting the facial expressions they can manage. Their brain to body ratio tends to be smaller, indicating a lower intelligence. Their brain's olfactory lobes are larger, lending to the notion that they have a stronger reliance on smell. Their snouts are generally elongated, giving them a dog
Dog
The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...
-like appearance, although this is true of some monkey
Monkey
A monkey is a primate, either an Old World monkey or a New World monkey. There are about 260 known living species of monkey. Many are arboreal, although there are species that live primarily on the ground, such as baboons. Monkeys are generally considered to be intelligent. Unlike apes, monkeys...
s, too. Strepsirrhines have a postorbital bar
Postorbital bar
The postorbital bar is a bone which runs around the eyesocket of strepsirrhine primates. This is in contrast to the higher primates, haplorrhine, which have evolved fully enclosed sockets to protect their eyes....
, unlike haplorrhines. The strepsirrhines have also retained the ability to enzymatically manufacture vitamin C, which has been lost by all the haplorrhines, including the Tarsiidae.
With the exception of the aye-aye
Aye-aye
The aye-aye is a lemur, a strepsirrhine primate native to Madagascar that combines rodent-like teeth and a special thin middle finger to fill the same ecological niche as a woodpecker...
, all strepsirrhines have a toothcomb
Toothcomb
A toothcomb is an anatomical structure found in strepsirrhine primates, which includes lemurs, lorises and galagos. A toothcomb consists of long, flat forward-angled teeth, and includes the lower incisors and the canine teeth...
—tightly clustered incisor
Incisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...
s and canine teeth—that is used for grooming. Another grooming adaptation is a toilet-claw
Toilet-claw
A toilet-claw is the specialized claw or nail on the foot of certain primates, used for personal grooming. All prosimians have a toilet claw, but the digit that is specialized in this manner varies. Tarsiers have a toilet claw on toe two and toe three...
on the second toe of all strepsirrhines, while the big toe is widely separated from the others, allowing a vise-like grip for locomotion.
About 75% of species are nocturnal and all of these have a tapetum
Tapetum lucidum
The tapetum lucidum is a layer of tissue in the eye of many vertebrate animals....
, a shiny, reflective layer in the backs of their eyes, although several diurnal
Diurnal animal
Diurnality is a plant or animal behavior characterized by activity during the day and sleeping at night.-In animals:Animals that are not diurnal might be nocturnal or crepuscular . Many animal species are diurnal, including many mammals, insects, reptiles and birds...
species, such as the ring-tailed lemur
Ring-tailed Lemur
The ring-tailed lemur is a large strepsirrhine primate and the most recognized lemur due to its long, black and white ringed tail. It belongs to Lemuridae, one of five lemur families. It is the only member of the Lemur genus. Like all lemurs it is endemic to the island of Madagascar...
, have it, as well. Many of the nocturnal species also have very sensitive hearing and ears they can move independently, allowing them to capture sounds even better.
Strepsirrhine reproduction differs greatly from haplorrhine reproduction. Instead of an individual cycle, strepsirrhines have a breeding season. They also have a litter of offspring and the females have a Y-shaped (bicornate) uterus and multiple sets of nipples.
Classification and evolution
Lemur
Lemurs are a clade of strepsirrhine primates endemic to the island of Madagascar. They are named after the lemures of Roman mythology due to the ghostly vocalizations, reflective eyes, and the nocturnal habits of some species...
s. The other two families are split with the loris
Loris
Loris is the common name for the strepsirrhine primates of the subfamily Lorisinae in family Lorisidae. Loris is one genus in this subfamily and includes the slender lorises, while Nycticebus is the genus for the slow lorises....
es, potto
Potto
The potto is a strepsirrhine primate from the Lorisidae family. It is the only species in genus Perodicticus...
s and the galago
Galago
Galagos , also known as bushbabies, bush babies or nagapies , are small, nocturnal primates native to continental Africa, and make up the family Galagidae...
s in the infraorder Lorisiformes
Lorisiformes
Lorisiformes are a group of primates found throughout Africa and Asia. Members of this infraorder include the galagos and the lorises. As strepsirrhines, they are related to the lemurs.* Order Primates** Suborder Strepsirrhini: non-tarsier prosimians...
.
As recently as 2005, the aye-aye
Aye-aye
The aye-aye is a lemur, a strepsirrhine primate native to Madagascar that combines rodent-like teeth and a special thin middle finger to fill the same ecological niche as a woodpecker...
was tentatively placed in its own infraorder (Chiromyiformes). It was uncertain whether this unique primate split off from the ancestral strepsirrhine line before the lemurs and lorises, or after. If the aye-aye represents a group that is ancestral to all the rest of Strepsirrhini, then it evolved away from the strepsirrhine line between 63 million years ago (mya) (when the strepsirrhines split from the primitive primate line) and 50 mya (the lemur/loris split). If Chiromyiformes is to be considered as the sister only to the lemurs, then it must have evolved after the lemur/loris split 50 mya. In 2008, the aye-aye and its family, Daubentonia, were placed back in infraorder Lemuriformes, making it the fifth lemur family. Molecular research had shown that Aye-ayes were basal to the lemuriform clade
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
.
Early classification schemes broke the Primate order into the suborders Prosimii (prosimian
Prosimian
Prosimians are a grouping of mammals defined as being primates, but not monkeys or apes. They include, among others, lemurs, bushbabies, and tarsiers. They are considered to have characteristics that are more primitive than those of monkeys and apes. Prosimians are the only primates native to...
s) and Anthropoidea (simian
Simian
The simians are the "higher primates" familiar to most people: the Old World monkeys and apes, including humans, , and the New World monkeys or platyrrhines. Simians tend to be larger than the "lower primates" or prosimians.- Classification and evolution :The simians are split into three groups...
s - monkeys and ape
Ape
Apes are Old World anthropoid mammals, more specifically a clade of tailless catarrhine primates, belonging to the biological superfamily Hominoidea. The apes are native to Africa and South-east Asia, although in relatively recent times humans have spread all over the world...
s). However, the prosimian tarsier
Tarsier
Tarsiers are haplorrhine primates of the genus Tarsius, a genus in the family Tarsiidae, which is itself the lone extant family within the infraorder Tarsiiformes...
s have been shown to be more closely related to the simian
Simian
The simians are the "higher primates" familiar to most people: the Old World monkeys and apes, including humans, , and the New World monkeys or platyrrhines. Simians tend to be larger than the "lower primates" or prosimians.- Classification and evolution :The simians are split into three groups...
s. The remaining "prosimians" are now placed in Strepsirrhini, and tarsiers are now united with anthropoids (simians) in Haplorrhini.
Some classifications split Strepsirrhini directly into four superfamilies: Daubentonioidea, Lemuroidea, Loroidea (including Cheirogaleidae) and Indroidea. However, significant evidence suggests Cheirogaleidae is not related to the lorises, and that Indridae is sister-group to Lemuridae.
The strepsirrhine phylogeny has also been elucidated by retrotransposon
Retrotransposon
Retrotransposons are genetic elements that can amplify themselves in a genome and are ubiquitous components of the DNA of many eukaryotic organisms. They are a subclass of transposon. They are particularly abundant in plants, where they are often a principal component of nuclear DNA...
presence/absence data
Retrotransposon Marker
Retrotransposon markers are retrotransposons that are used as cladistic markers.The analysis of SINEs – Short INterspersed Elements – LINEs – Long INterspersed Elements – or truncated LTRs – Long Terminal Repeats – as molecular cladistic markers represents a particularly interesting complement to...
.
The adapid
Adapid
Adapids are a diverse group of extinct primates that primarily radiated during the Eocene epoch between about 55 and 34 million years ago. However, one specialized endemic Asian group survived into the Miocene. Fossils of adapids are known from North America, Europe, Asia, and Africa...
s are an extinct polyphyletic grouping that were most certainly prosimian
Prosimian
Prosimians are a grouping of mammals defined as being primates, but not monkeys or apes. They include, among others, lemurs, bushbabies, and tarsiers. They are considered to have characteristics that are more primitive than those of monkeys and apes. Prosimians are the only primates native to...
s and closely related to the strepsirrhines. The omomyid
Omomyid
Omomyids are a diverse group of early primates that radiated during the Eocene epoch between about 55 and 34 million years ago . Fossils of omomyids are found in North America, Europe, Asia, and possibly Africa...
s are another extinct group of prosmians, but they are believed to be haplorrhines, closely related to the tarsiers, but an outgroup to the rest of the haplorrhines.
As of 2010, there are 125 species of extant strepsirrhine primates, over three-quarters of which are lemurs from Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
.
- Order PrimatePrimateA primate is a mammal of the order Primates , which contains prosimians and simians. Primates arose from ancestors that lived in the trees of tropical forests; many primate characteristics represent adaptations to life in this challenging three-dimensional environment...
s- Suborder Strepsirrhini: Non-tarsier prosimians
- Infraorder Lemuriformes
- Family CheirogaleidaeCheirogaleidaeCheirogaleidae is the family of strepsirrhine primates that contains the various dwarf and mouse lemurs. Like all other lemurs, cheirogaleids live exclusively on the island of Madagascar.-Characteristics:...
: Dwarf and mouse lemurs (30 species) - Family DaubentoniidaeAye-ayeThe aye-aye is a lemur, a strepsirrhine primate native to Madagascar that combines rodent-like teeth and a special thin middle finger to fill the same ecological niche as a woodpecker...
: Aye-aye (1 species) - Family LemuridaeLemuridaeLemuridae is a family of prosimian primates native to Madagascar, and one of five families commonly known as lemurs. These animals were thought to be the evolutionary predecessors of monkeys and apes, but this is no longer considered correct...
: Lemurs (22 species) - Family Lepilemuridae: Sportive lemurs (25 species)
- Family IndriidaeIndriidaeThe Indriidae are a family of strepsirrhine primates. They are medium to large sized lemurs with only four teeth in the toothcomb instead of the usual six...
: Woolly lemurs and allies (19 species)
- Family Cheirogaleidae
- Infraorder LorisiformesLorisiformesLorisiformes are a group of primates found throughout Africa and Asia. Members of this infraorder include the galagos and the lorises. As strepsirrhines, they are related to the lemurs.* Order Primates** Suborder Strepsirrhini: non-tarsier prosimians...
- Family LorisidaeLorisidaeLorisidae is a family of strepsirrhine primates. The lorisids are all slim arboreal animals and include the lorises, pottos and angwantibos. Lorisids live in tropical, central Africa as well as in south and southeast Asia....
: Lorises, pottos and allies (9 species) - Family Galagidae: Galagos (19 species)
- Family Lorisidae
- Infraorder Lemuriformes
- Suborder HaplorrhiniHaplorrhiniThe haplorhines, the "dry-nosed" primates , are members of the Haplorhini clade: the prosimian tarsiers and the anthropoids...
: Tarsiers, monkeys and apes
- Suborder Strepsirrhini: Non-tarsier prosimians